The present disclosure is directed to toner compositions containing a white colorant and processes of making thereof. More specifically, the toner compositions include toner particles having a high loading of white colorants, such as, for example, greater than 30% by weight of the toner, and exhibit high lightness values. In embodiments, the toner compositions are suitable for use in offset lithography (or offset printing). Lithography is common for use in digital label press and packaging printing.
In the offset process, the image may be indirectly applied to the media, such as paper or other materials, through an intermediate transfer, or blanket cylinder, whereby the image from the plate is applied first to a blanket cylinder, which then offsets, or transfers, from the blanket cylinder to the media.
In order to compete effectively with offset printing, or for high quality color applications or for special effects, lithographic printers often add a fifth xerographic station to enable gamut extension via the addition of a fifth color. At any given time, the lithographic printing machine runs CMYK toners plus a fifth color in the fifth station, depending on the color space where the gamut extension is desired. A fifth color is any spot color used in addition to the four color CMYK mix (Cyan, Magenta, Yellow and Black).
White toners can be used as the fifth color for color gamut enhancement. White toner has the ability to make the colors light and to extend the upper part of the spot color gamut in the high L* range, where L* is a measure of the lightness of the color.
In current high speed production electrophotography of xerography printing, the color gamut for high L* region is limited by the white pigment loading of the toner particles. Thus, there is a need for a white toner with high pigment loading to produce white images on black substrates with an L* close to 75 or higher either by single or multiple pass development.